1. Field
The present embodiments relate to a liquid crystal display device and method for driving the same.
2. Related Art
Conventionally, cathode-ray tubes (CRTs) have been widely used as display devices. Research and development of various types of flat panel displays as a substitutes for CRTs has been conducted. For example, liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays (FED), and electro-luminescence displays (ELDs) have been developed. These flat panel displays are driven by an active matrix driving method with a plurality of pixels arranged in a matrix configuration that are driven using a plurality of thin film transistors therein. Among these active matrix type flat panel displays, liquid crystal display (LCD) devices and electroluminescent display (ELD) devices are widely used for notebook computers and desktop computers because of their high resolution, ability to display colors and superiority in displaying moving images.
Generally, an LCD device includes two substrates that are spaced apart and face each other with a layer of liquid crystal molecules interposed between the two substrates. The two substrates include electrodes that face each other. A voltage is applied between the electrodes that induce an electric field across the layer of liquid crystal molecules. The alignment of the liquid crystal molecules changes in accordance with the intensity of the induced electric field, for example, changes the light transmissivity of the LCD device. The LCD device displays images by varying the intensity of the electric field across the layer of liquid crystal molecules.
As shown in FIGS. 1 and 2, a LCD device includes a liquid crystal panel 2, a driving circuit 26, an interface 10 and a power supply 14. The driving circuit 26 includes gate and data drivers 20 and 18, a timing controller 12, and a gamma reference voltage generator 16.
A liquid crystal panel 2 includes a plurality of gate lines GL1 to GLn along a row direction and a plurality of data lines DL1 to DLm along a column direction. The gate lines GL1 to GLn and the data lines DL1 to DLm cross each other to define a plurality of pixels. Each pixel includes a thin film transistor TFT and a liquid crystal capacitor LC. The liquid crystal capacitor LC includes a pixel electrode, a common electrode and a liquid crystal layer between the pixel and common electrodes.
Data signals and control signals are inputted into the interface 10 from an exterior system such as a computer. The data signals and control signals are, for example, a vertical synchronization signal (vsync), a horizontal synchronization signal (hsync) and/or a data clock (dck). The interface 10 supplies the data and control signals to the timing controller 12. The timing controller 12 generates control signals that control the gate and data drivers 20 and 18 and supplies data signals to the data driver 18. The gamma reference voltage generator generates gamma reference voltages used for a DAC (digital to analog converter) in the data driver 18.
The data driver 18 outputs data voltages corresponding to the data signals to the data lines DL1 to DLm. The gate driver 2 outputs gate voltages to the gate lines GL1 to GLn.
On-level gate voltages are sequentially applied to the gate lines GL1 to GLn to enable the gate lines GL1 to GLn and the thin film transistors TFT connected to the gate lines GL1 to GLn. For example, when the thin film transistors TFT are turned on, the data voltages are applied to the pixels through the data lines DL1 to DLm. Accordingly, an electric field is applied to the liquid crystal and the light transmissivity of the liquid crystal layer changes, thereby displaying images.
A power supply 14 generates driving voltages for the driving circuit 26 and the common voltage for the common electrode of the liquid crystal panel 2.
The driving circuit 26 is formed directly in the liquid crystal panel 2 using a low temperature poly-crystalline silicon (LTPS) method.
Generally, the data driver is operated with an 8-bit driving method instead of 6-bit driving method. When the LTPS method is applied to the LCD device with the 8-bit driving method, the LCD device with the 8-bit driving method needs more space for the driving circuit than the LCD device with the 6-bit driving method. This causes inefficiency of the space for the driving circuit, difficulty of panel design, increase of product cost and the like.